Boulder Study Examines How The Stink Eye May Be A Survival Tool

Jun 19, 2017

You can tell a lot about someone just by looking into their eyes, according to a new study out of the University of Colorado - Boulder. That’s by design.

Eye and facial expressions are actually a survival tool, as they occur faster than people can communicate verbally, said CU-Boulder researcher and lead author Daniel Lee.

“We know that our eyes are extremely important for social signaling, but to understand why that is you have to go back to Darwin’s theories,” Lee said. “Our research suggests these expressions evolved for functional reasons first — to help the expresser gather more information and enhance his or her chances for survival — and were later co-opted as communication tools.”

But those tools actually benefit others more than they benefit you.

“We’re really social and the eyes seem to be a good signal for conveying all sorts of things,” Lee said. “There’s a reason for your eye whites and they don’t really help you, they help other people. They act as a signal enhancer that contrast your iris, which tells me where you’re looking.”

That can be particularly helpful in dangerous situations when the facial expression is fear. When you’re face-to-face with someone and you see their eyes widen in fear, you know there is potential danger behind you, he said.

But it’s not all about helping others. When expressing fear, the mouth stretches and the eyes widen.

“It has this quality of stretching out your face and your sensory apertures to gather more sensory information about the world,” Lee said. “Versus a disgust expression [which] does the opposite of scrunching up your face. There’s this nose wrinkle and a lip raise that seem to be more about rejecting sensory information.”

In addition, when someone finds something objectionable, they typically squint their eyes, which allows them to see things in greater detail, and thus be better able to determine if something could be harmful.

In the study, subjects were shown composites of eye expressions along with varying facial expressions on a computer screen. When looking at the eyes alone, the subjects got the emotion right 90 percent of the time. Even when the lower part of the face was shown with a mismatched expression, the subjects still got it right most of the time.

Using the participants answers, researchers developed a “mental-state map” to show exactly which eye features equated to certain emotions. Eventually, Lee said he hopes the study will help people with autism or others with difficulty reading emotional cues.